Renal oxidative stress is determined by the balance between the primary source of superoxide, NADPH oxidase (NOX) and intrarenal enzymes that scavenge superoxide, superoxide dismutases (SOD). Renal oxidative stress contributes to the development of systemic hypertension by alterations in renal function, including vasoconstriction, increased solute and electrolyte retention and tubular dysfunction. The reabsorption of sodium is the major energy requirement for the kidney and the efficient use of oxygen for Na+ transport is reduced during oxidative stress. We propose to test the effects of oxidative stress on oxygen usage in the kidney and to determine the mechanism(s) by which Na+ reabsorption requires greater oxygen. In a series of experiments measuring in vivo single nephron function in gene deleted mice and in vitro measurements of PT cell function we will identify specific sites of oxygen utilization dysfunction. In aim 1, we will test the hypothesis that the inefficient use of oxygen is dependent on the balance between NOX and SOD, by using single gene deleted mice. In aim 2 we will examine the mechanism of the inefficient use of oxygen, focusing on Na+ reabsorption in the proximal tubule (PT). In a series of both in vivo and in vitro experiments, we will evaluate the cellular integrity and function of the PT during acute and chronic oxidative stress. We will examine paracellular and transcellular function in PT cells. In aim 3 we will test the hypothesis that the increased blood pressure associated with angiotensin II-induced oxidative stress is dependent on increased generation of adenosine and enhancement of tubuloglomerular feedback, leading to decreased renal blood flow and increased renal vascular resistance. These studies should provide new and valuable information on the relationship between oxygen usage in the kidney and the pro-vasoconstriction events associated with oxidative stress and hypertension. Project Narrative: Ischemia, the lack of efficient oxygen delivery is the most common cause of acute renal failure and renal artery stenosis causing renal ischemia is the second most common cause of secondary hypertension. These conditions are accompanied by severe oxidative stress within the kidneys. Therefore, knowledge of the interaction of oxidants and oxygen within the kidney will provide insight into the causes of these renal diseases.